Spinal rod approximator

ABSTRACT

Spinal implants, spinal rod approximators for seating a stabilizing rod in a rod-receiving portion of a spinal implant, and methods for using the same are provided. In one embodiment, a spinal rod approximator is provided including an elongate member having a grasping member formed on a distal end thereof, and a rod pusher member slidably mated to or mounted on the elongate member. The grasping member is effective to grasp a portion of a spinal implant, and the pusher member is effective to grasp and engage a stabilizing rod and push the rod into a rod-receiving portion of the spinal implant being grasped by the grasping member.

FIELD OF THE INVENTION

[0001] The present invention relates to spinal fixation systems, and in particular to a spinal rod approximator, a spinal implant, and methods for using the same.

BACKGROUND OF THE INVENTION

[0002] Spinal fixation devices are used in orthopedic surgery to align and/or fix a desired relationship between adjacent vertebral bodies. Such devices typically include a spinal fixation element, such as a relatively rigid fixation rod, that is coupled to adjacent vertebrae by attaching the element to various anchoring devices, such as hooks, bolts, wires, or screws. The fixation rods can have a predetermined contour that has been designed according to the properties of the target implantation site, and once installed, the instrument holds the vertebrae in a desired spatial relationship, either until desired healing or spinal fusion has taken place, or for some longer period of time.

[0003] Spinal fixation devices can be anchored to specific portions of the vertebra. Since each vertebra varies in shape and size, a variety of anchoring devices have been developed to facilitate engagement of a particular portion of the bone. Pedicle screw assemblies, for example, have a shape and size that is configured to engage pedicle bone. Such screws typically include a threaded shank that is adapted to be threaded into a vertebra, and a head portion having a rod-receiving element, usually in the form of a U-shaped slot formed in the head. A set-screw, plug, or similar type of fastening mechanism, is used to lock the fixation rod into the rod-receiving portion of the pedicle screw. In use, the shank portion of each screw is then threaded into a vertebra, and once properly positioned, a fixation rod is seated through the rod-receiving portion of each screw and the rod is locked in place by tightening a cap or similar type of locking mechanism to securely interconnect each screw and the fixation rod.

[0004] While current spinal fixation systems have proven effective, difficulties have been encountered in mounting rods into the rod-receiving portion of various fixation devices. In particular, it can be difficult to align and seat the rod into the rod receiving portion of adjacent fixation devices due to the positioning and rigidity of the vertebra into which the fixation device is mounted. Thus, the use of a spinal rod approximator, also referred to as a spinal rod reducer, is often required in order to grasp the head of the fixation device, and reduce the rod into the rod-receiving portion of the fixation device.

[0005] While several rod approximators are known in the art, some tend to be difficult and very time-consuming to use. Accordingly, there is a need for an improved rod approximator, implants for use with rod approximators, and methods for seating a spinal rod in a rod-receiving portion of one or more spinal implants.

SUMMARY OF THE INVENTION

[0006] The present invention provides medical devices and methods for seating a stabilizing rod in a rod-receiving portion of a spinal implant, and spinal implants for use with a rod approximator. In one embodiment, a rod approximator device is provided including an elongate member having a proximal end and a distal end defining an axis extending therebetween, and a grasping member extending from the distal end of the elongate member in a direction substantially transverse to the axis. The grasping member is effective to engage a spinal implant, and can optionally define opposed arms adapted to slide into and engage corresponding slots formed in a spinal implant. The device further includes a rod pusher member slidably mated to the elongate member and movable along the axis between a first position in which the rod pusher member is positioned a distance apart from the grasping member and is effective to grasp a stabilizing rod, and a second position in which the rod pusher member is positioned adjacent to the grasping member and is effective to position the grasped stabilizing rod in a rod-receiving portion of a spinal implant being engaged by the grasping member.

[0007] The rod approximator device of the present invention can also include an actuating member that can be coupled to the proximal end of the elongate member and the rod pusher member. The actuating member is effective to move the rod pusher member with respect to the grasping member. The actuating member can have a variety of configurations and in one embodiment it comprises opposed first and second members. A force applied to bring the first and second members toward one another is effective to move the rod pusher member from the first position to the second position. The actuating member can extend in a direction substantially transverse to the axis of the elongate member, and can optionally extend in a direction opposed to the grasping member. In an exemplary embodiment, the actuating member is in the form of a handle or grip and it comprises a first, stationary member mated to the proximal end of the shaft, and a second, opposed movable member linked to the proximal end of the elongate member. A force applied to bring the second, movable member toward the first, stationary member is effective to move the rod-engaging member from the first position to the second position. The actuating member can optionally include a ratchet mechanism effective to move the rod pusher member from the first position to the second position in predetermined increments. A release mechanism can be coupled to the ratchet mechanism to release the ratchet mechanism to enable the rod pusher member to return to the first position. The device can also optionally include a locking mechanism effective to lock the actuating member in one of the first or second positions, or optionally in an intermediate position between the first and second positions.

[0008] The rod pusher member of the approximator device can also have a variety of configurations. In one embodiment, the rod pusher member can include a shaft having proximal and distal ends, and can be slidably mounted on the elongate member along the axis. The rod pusher member can also include a rod-engaging member mated to the distal end of the shaft and preferably offset a distance apart from the shaft in a direction substantially transverse to the axis. The rod-engaging member can have a substantially semi-cylindrical shape and can include at least one rod-engaging recess formed on a distal facing portion thereof. In an exemplary embodiment, the grasping member defines opposed arms adapted to slide into and engage corresponding slots formed in a spinal implant, and at least one rod-engaging recess is formed in the rod-engaging member and is axially aligned with the opposed arms of the grasping member.

[0009] In another embodiment of the present invention, a system for seating a stabilizing rod in a rod-receiving portion of a spinal implant is provided. The system includes a spinal implant having a distal, bone engaging portion, and a proximal head including a base portion mated to the distal, bone engaging portion. A rod-receiving recess is formed in the proximal head for seating a stabilizing rod. The system further includes a rod reduction device having an elongate member with a distal grasping member formed thereon and offset from a longitudinal axis of the elongate member. The grasping member is adapted to engage and grasp the base portion of the head of the spinal implant. The rod reduction device also includes a rod pusher member slidably mounted on the elongate member and effective to grasp a stabilizing rod and, upon actuating, to push the rod into the rod-receiving recess formed in the spinal implant.

[0010] In an exemplary embodiment, the distal grasping member is substantially U-shaped, and the base portion of the head of the implant includes opposed slots formed therein. Preferably, the grasping member is adapted to slide into the slots on the implant to grip the implant. The opposed slots formed in the base portion of the head of the spinal implant can have a variety of configurations. In one embodiment, the slots each include an upper and lower shoulder. The lower shoulder is preferably substantially planar, and the upper shoulder is preferably substantially planar and includes opposed ends that are curved in a direction away from the lower shoulder. In other aspects of the invention, the head of the spinal implant can have a substantially hollow, cylindrical shape and can include opposed cut-out portions that form the rod-receiving recess for seating a stabilizing rod. The opposed slots formed in the base portion of the head of the spinal implant are preferably positioned distally adjacent to the opposed cut-out portions formed in the head of the spinal implant.

[0011] In yet another embodiment, the rod pusher member comprises an elongate shaft having proximal and distal ends that extend along the longitudinal axis, and a rod-engaging member mated to the distal end of the shaft and offset a distance apart from the axis of the shaft. An actuating member can be mated to the elongate member and the rod pusher member, and is effective to selectively move the rod pusher member between a first position in which the rod-engaging member is offset a distance apart from the grasping member, and a second position in which the rod-engaging member is positioned adjacent to the grasping member and is effective to position a stabilizing rod in the rod-receiving recess formed in the head of the spinal implant that is being engaged by the grasping member. In a preferred embodiment, the actuating member extends in a direction substantially transverse to the axis, and more preferably, the actuating member extends in a direction opposed to the grasping member.

[0012] In yet another embodiment of the present invention, a spinal implant is provided having a substantially hollow, cylindrical shaped head member including an open, proximal end and a closed, distal end. A bone-engaging member extends from the closed, distal end of the head member and is effective to engage bone. The head member includes a rod-receiving recess formed from opposed cut-out portions extending from the open, proximal end and terminating proximal to the closed, distal end. The head further includes opposed slots formed in a base of the head proximal to the closed, distal end and distal to the cut-out portions. The opposed slots are effective to receive opposed arms of a rod reduction device to enable the rod reduction device to engage the head of the spinal implant and to engage a stabilizing rod to push the rod into the rod-receiving recess formed in the head of the spinal implant.

[0013] The opposed slots formed in the base portion of the head of the spinal implant can each include an upper and lower shoulder. The lower shoulder is preferably substantially planar, and the upper shoulder is preferably substantially planar and includes opposed ends that are curved in a direction away from the lower shoulder.

[0014] Methods for reducing a stabilizing rod into a rod-receiving portion of a spinal implant are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0016]FIG. 1 is perspective view illustration of a spinal rod approximator according to one embodiment of the present invention;

[0017]FIG. 2 is a perspective view illustration of the grasping member of the device shown in FIG. 1;

[0018]FIG. 3A is a perspective view illustration of one embodiment of the grasping portion formed on the distal end of the grasping member shown in FIG. 2;

[0019]FIG. 3B is a perspective view illustration of another embodiment of the grasping portion formed on the distal end of the grasping member shown in FIG. 2;

[0020]FIG. 3C is a perspective view illustration of yet another embodiment of a grasping portion of a grasping member according to the present invention;

[0021]FIG. 3D is a side view illustration of the grasping portion shown in FIG. 3C;

[0022]FIG. 4 is perspective view illustration of the rod pusher member of the device shown in FIG. 1;

[0023]FIG. 5 is a perspective view illustration of one embodiment of the rod-engaging portion formed on the distal end of the rod pushing member shown in FIG. 4;

[0024]FIG. 6A is a side view illustration of the distal portion of a rod approximator device in a non-actuated position;

[0025]FIG. 6B is a side view illustration of the distal portion of the rod approximator device shown in FIG. 6A in the actuated position;

[0026]FIG. 7 is a sectional view illustration of the spinal rod approximator shown in FIG. 1 according to the present invention;

[0027]FIG. 8 is a perspective view illustration of another embodiment of a spinal rod approximator according to the present invention;

[0028]FIG. 9 is a perspective view illustration of the grasping member of the device shown in FIG. 8;

[0029]FIG. 10 is a perspective view illustration of one embodiment of the rod-engaging portion formed on the distal end of the rod pushing member shown in FIG. 8; and

[0030] FIGS. 11A-11C are perspective view illustrations of a spinal implant according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0031] In general, the present invention provides spinal fixation systems, and in particular a spinal implant, a spinal rod approximator for seating a stabilizing rod in a rod-receiving portion of a spinal implant, and methods for using the same. The spinal implants and spinal rod approximators of the present invention are particularly effective in that they are easy to use, they do not require significant force to operate, and they are efficient, thereby reducing the time and expense necessary to perform spinal surgery.

[0032]FIG. 1 illustrates one embodiment of a spinal rod approximator 10 that is effective to engage and seat a stabilizing rod in a rod-receiving portion of a spinal implant. As shown, the tool 10 generally includes an elongate member 12 having a grasping member 14 formed on a distal end thereof, and a rod pusher member 16 slidably mated to or mounted on the elongate member 12. The grasping member 14 is effective to grasp a portion of a spinal implant, and the pusher member 16 is effective to grasp and engage a stabilizing rod and push the rod into a rod-receiving portion of the spinal implant being grasped by the grasping member 14.

[0033] A person having ordinary skill in the art will appreciate that while the tools and devices illustrated herein are described for use with spinal surgery, the tools can be adapted for use with a variety of medical procedures.

[0034] The elongate member 12 of the rod approximator 10 is shown in more detail in FIG. 2. The elongate member 12 can have a variety of shapes and sizes, but is preferably a generally elongate, solid rigid member having a proximal end 12 a and a distal end 12 b. The cross-sectional shape and size of the elongate member 12, as well as the length l_(e) of the elongate member 12, can vary depending on the intended use. The elongate member 12 should, however, be substantially rigid to prevent bending thereof, and should have a length 1 _(e) sufficient to enable the distal end 12 b of the elongate member 12 to be placed adjacent to a surgical site while the proximal end 12 a of the elongate member 12 remains outside a patient's body. By varying the size and shape, the elongate member 12 can also be adapted for use in minimally invasive procedures. By way of non-limiting example, the elongate member 12 can be configured to be disposed through an access tube or similar device.

[0035] The distal end 12 b of the elongate member 12 includes a mating element 14 that is effective to grasp a spinal implant. The mating element 14 can have a variety of configurations, but is preferably a U-shaped grasping member 14 that is effective to grasp and engage a spinal implant. The grasping member 14 can be mated to the distal end 12 a of the elongate member 12 using a variety of mating techniques, or it can be integrally formed thereon. Preferably, the grasping member 14 is integrally formed with the elongate member 12, and extends in a direction substantially transverse to an axis A of the elongate member 12. The grasping member 14 can also be positioned at a distance offset from the axis A of the elongate member 12 to facilitate use of the device. The offset position is particularly advantageous in that the implant can be grasped by the device while avoiding contact with adjacent bone structures. The offset position can be formed by providing a bend 15 in the distal end 12 b of the elongate member 12, as shown in FIGS. 2-3B. While the angle α of the bent portion with respect to the axis A of the elongate member 12 can vary, the angle α is preferably in the range of about 15° to 60°, and more preferably is about 45° with respect to the axis A.

[0036] Still referring to FIGS. 3A and 3B, the grasping member 14 is adapted to mate with corresponding mating elements formed on the head portion of a spinal implant, as will be discussed in more detail with respect to FIGS. 11A-11C. While the grasping member 14 can have a variety of configurations, FIG. 3A illustrates one embodiment of a grasping member 14 having opposed arms 22 a, 22 b that extend outward from a semi-cylindrical wall 31 in a direction substantially perpendicular to the axis A of the elongate member 12. The semi-cylindrical wall contoured to the head of an implant being engaged, and it is adapted to fit around and seat the head of the implant. Further, the arms 22 a, 22 b are configured to fit within corresponding recesses or slots formed in the head of the implant.

[0037] Each arm 22 a, 22 can have virtually any shape and size, and the arms can include several different mating features to facilitate grasping of the implant. As shown, the opposed arms 22 a, 22 b have a generally elongate, rectangular shape and include opposed proximal and distal surfaces 24 a, 24 b, 26 a, 26 b, and opposed inner 24 c, 26 c and outer 24 d, 26 d side surfaces, respectively. The proximal and distal surfaces 24 a, 24 b, 26 a, 26 b, and opposed inner 24 c, 26 c and outer 24 d, 26 d side surfaces are each preferably substantially planar. The distal most end 28 a, 28 b of each arm 22 a, 22 b can be rounded to facilitate insertion of the arms 22 a, 22 b into the corresponding slots formed in the head of the implant, and to prevent any potential damage to tissue surrounding the treatment site. Each arm of the grasping member can also optionally include a curved and/or narrowed distal tip 28 a, 28 b. Preferably, the proximal surface 24 a, 26 a of each arm 22 a, 22 b is ramped such that the distal tip 28 a, 28 b of each arm has a width less than a width of the proximal portion of the arm 22 a, 22 b. The narrowed tip allows the arms to be inserted into corresponding slots formed in a spinal implant at a variety of angles, thereby facilitating use of the device.

[0038]FIG. 3B illustrates another embodiment of a grasping member 14′ that includes an inner recess 32 formed thereon that is adapted to receive a corresponding ridge formed around a base portion of the spinal implant. As shown, the recess 32 is formed around the distal most portion of the inner surface of the grasping member 14′, and extends around the inside of both arms 22 a′, 22 b′ and optionally can extend around the semi-cylindrical wall 31′. The inner wall 34 is preferably slightly concave so as to be contoured to the rounded shape of the head of the implant. In use, an annular ridge formed around the head of the spinal implant slides into the recess 32 and the inner wall 34 fits securely around the base portion of the implant to allow the grasping member 14′ to engage the implant.

[0039] FIGS. 3C-3D illustrate yet another embodiment of a grasping member 90 having a pin and bore connection. As shown, the distal end 93 of the elongate member 92 includes a pin 94 disposed thereon that extends in a direction transverse to the axis a. The pin 94 preferably extends toward the proximal end 91 of the elongate member 92 at an angle α′ with respect to the axis a, and has a shape and size adapted to fit within a corresponding bore 96 formed in the head 98 of the implant. The pin 94 and the bore 96 can have virtually any shape and size, but the pin 94 should be configured to securely grasp the head 98 of the implant when inserted in the bore 96. The angle α′ of the pin 94 facilitates a secure engagement of the head 98 as the angle α′ prevents the pin 94 from falling out of the bore 96 when a proximally-directed force is applied to the elongate member 92.

[0040] A person having ordinary skill in the art will appreciate that the grasping members 14, 14′, 90 shown in FIGS. 3A-3C are not intended to limit the scope of the invention. The grasping member can significantly vary in shape and size, and can be, for example, square or oval. The term “U-shaped” is intended to include any grasping member that is effective to grasp and engage an implant, and is not limited to grasping members having a U-shape. The grasping member and/or the head of the spinal implant can also include a variety of mating elements, including tongue-and-groove connections, dovetail connections, etc. Alternatively, the grasping member can be formed from, for example, opposed pin-type members that are adapted to fit within corresponding bores formed in the head of an implant. The arms can also optionally be slightly flexible to allow the arms to snap-around a portion of the head of a spinal implant.

[0041]FIG. 4 illustrates the rod pusher member 16 which is slidably mounted on and/or mated to the elongate member 12, and is effective to engage and push a spinal rod toward the grasping member 14 to seat the rod in a rod-receiving portion of an implant being engaged by the grasping member 14. The rod pusher member 16 can also have a variety of configurations, but is preferably a generally elongate rigid member having a proximal end 16 a and a distal end 16 b. The size and cross-sectional shape of the rod-pusher member 16 can vary, but preferably the rod-pusher member 16 has a generally cross-sectional shape and includes a substantially planar mounting surface 36 adapted to rest on the elongate member 12. The length l_(r) of the rod pusher member 16 can also vary, but preferably the rod pusher member 16 has a length l_(r) less than the length l_(e) of the elongate member 12.

[0042] The rod pusher member 16 can be mated to the elongate member 12 using a variety of mating techniques. By way of non-limiting example, the rod pusher member 16 can include a channel or groove (not shown) formed therein, and the elongate member 12 can include a corresponding tongue (not shown) formed thereon and adapted to be slidably disposed within the groove. A person having ordinary skill in the art will appreciate that virtually any mating technique can be used to slidably mate the rod pusher member 16 to the elongate member 12.

[0043] The distal end 16 b of the rod pusher member 16 is adapted to engage a spinal fixation rod, and thus can include a rod-engaging member 18 formed thereon. The rod-engaging member 18 can have a variety of configurations, and can be positioned adjacent to the grasping member 14, or can be offset from the grasping member 14. The rod-engaging member 18 can be integrally formed on the distal end 16 b of the rod pusher member 16, or alternatively it can be removably mated to the rod pusher member 16. The rod-engaging member 18 can also optionally be adjustably mounted onto the rod pusher member 16 to allow the length 1 r of the rod pusher member 16 to be adapted based on the intended use of the device.

[0044]FIG. 5 illustrates one embodiment of a rod-engaging member 18 having opposed arms 38 a, 38 b that are adapted to engage and push a rod toward the grasping member 14. The arms 38 a, 38 b are preferably mated to a T-shaped member 44 formed on the distal end 16 b of the rod pusher member 16, and each arm 38 a, 38 b is preferably positioned a distance d apart from one another to allow the arms 38 a, 38 b to be positioned around the head of an implant, and to allow access to a rod-receiving portion formed in the head of the spinal implant being engaged by the grasping member 14. The arms 38 a, 38 b are each also preferably aligned with the arms 22 a, 22 b of the grasping member 14, and they preferably extend in a direction substantially perpendicular to the T-shaped member 44. The arms 38 a, 38 b and the T-shaped member 44 can have a substantially semi-cylindrical shape, or can have a variety of other shapes.

[0045] Each arm 38 a, 38 b itself can also vary in shape and size, but preferably each arm is substantially planar and has a generally ramp-like shape such that width w of each arm 38 a, 38 b, extending in a direction transverse to the axis A, increases from the proximal end 40 a, 40 b to the distal, rod-engaging end 42 a, 42 b. The ramp-like shape of the arms 38 a, 38 b facilitates access to the rod-receiving portion of the spinal implant.

[0046] The distal, rod-engaging end 42 a, 42 b of each arm 38 a, 38 b can include a recess 46 a, 46 b formed therein for seating a stabilizing rod. The recesses 46 a, 46 b can have virtually any shape, such as square or semi-cylindrical. The recesses 46 a, 46 b can also be generally elongated to facilitate grasping of the stabilizing rod.

[0047] A person having ordinary skill in the art will appreciate that the rod pusher member can have a variety of configurations, but should be adapted to grasp and push a spinal fixation rod into a rod-receiving portion of a spinal implant.

[0048] In use, the rod pusher member 16 is movable between a first proximal position, shown in FIG. 6A, in which the distal end 16 b of the rod pusher member 16 is positioned proximal to and a distance apart from the grasping member 14 formed on the distal end 12 b of the elongate member 12, and a second position, shown in FIG. 6B, in which the distal end 16 b of the rod pusher member 16 is positioned adjacent to, or is in contact with, the grasping member 14. In the first position, the rod pusher member 16 is effective to grasp a spinal fixation rod R. The rod pusher member 16 can then be moved to the second position to push the rod R into a rod receiving portion 48 of a spinal implant I being engaged by the grasping member 14.

[0049] In order to move the rod pusher member 16 between the first and second positions, the proximal end 12 a of the elongate member 12 and the proximal end 16 a of the rod pusher member 16 can be mated to an actuating member 50. The actuating member 50 can extend along the axis A of the device 10, but it preferably extends in a direction substantially transverse to the axis A. More preferably, the actuating member 50 can be a handle or grip-like element that extends in a direction opposed to the grasping member 14 and the rod engaging member 18. This configuration provides better visual access to the surgical site.

[0050] While virtually any actuating member can be used with the present invention, FIGS. 1 and 7 illustrate a preferred embodiment of an actuating member 50 having first and second opposed handle members 52, 54. The first handle member 52 is mated to or formed integrally with the proximal end 12 a of the elongate member 12, and the second handle member 54 is linked to the proximal end 16 a of the rod pusher member 16. Both of the handle members 52, 54 can be movably mated to one another, but preferably the first handle member 52 is stationary and fixedly attached to the elongate member 12, and the second handle member 54 is pivotally mated to the first handle member 52 and to the rod pusher member 16. As shown, the handle members 52, 54 are mated to one another at pivot point P. The second handle member 54 is adapted to rotate at pivot point P, and is mated to the rod pusher member 16 to move the rod pusher member 16 between the first and second positions. As shown, the second handle member 54 includes a distal end 62 that extends into a slot 64 formed in the rod pusher member 16. Movement of the handle 54 from the non-actuated position, shown in FIG. 1, to the actuated position, shown in FIG. 7, causes the distal end 62 of the handle 54 to engage the slot 64 and move the rod pusher member 16 in a distal direction. A person having ordinary skill in the art will appreciate that a variety of techniques can be used to effect movement of the rod pusher member 16.

[0051] The actuating member 50 can also optionally include a biasing element 56 disposed between the handle members 52, 54. The biasing element 56 is preferably effective to bias the first and second handle members 52, 54 to an open position, as shown in FIG. 1, wherein the rod-engaging member 18 is positioned a distance apart from the grasping member 14. A force can be applied to the first and second handle members 52, 54 to overcome the biasing force of the biasing element 56, and thereby move the rod pusher member 16 from the first, proximal position to the second, distal position. A variety of biasing elements 56 can be used with the actuating member 50 including, for example, spring mechanisms. As shown in FIGS. 1 and 7, the biasing element 56 is formed from opposed flexible members that force the first and second members into the open position.

[0052] A person having ordinary skill in the art will appreciate that virtually any actuating member can be used to move the rod-pusher member 16 and/or the elongate member 12 between the open and closed positions. By way of non-limiting example, the device 10 can include a ratchet-type mechanism having a trigger that, upon actuating, is effective to move the rod pusher member 16 in a distal direction in predetermined increments with respect to the elongate member 12. The device 10 can also optionally include a locking mechanism effective to lock the device 10 in the second, actuated position. A person having ordinary skill in the art will appreciate that the device can include a variety of other features to facilitate use of the device.

[0053] FIGS. 8-10 illustrate another embodiment of a spinal rod approximator 210 in which the rod reducer member 218 is substantially parallel to the axis a, rather than offset from the axis, as shown in FIG. 1 of rod reducer 10. Except as otherwise discussed herein, rod approximator 210 is substantially the same as rod approximator 10, and the elements of rod reducer 210 that are the same as the elements of rod reducer 10 are similarly designated but have a prefix “2” added to the reference numeral used for that element in the description of rod reducer 210. As shown in FIG. 8, rod reducer 210 includes an elongate member 212 having a grasping member 214 formed on a distal end thereof, and a rod pusher member 216 slidably mated to or mounted on the elongate member 212. The grasping member 214 is effective to grasp a portion of a spinal implant, and the pusher member 216 is effective to grasp and engage a stabilizing rod and push the rod into a rod-receiving portion of the spinal implant being grasped by the grasping member 214.

[0054] The grasping member 214 is shown in more detail in FIG. 9 and includes a first, upright portion 221 that extends along the longitudinal axis a of the device 210, and a second portion 227 having opposed arms 222 a, 222 b that extend in a direction substantially perpendicular to the upright portion 221. The upright portion 221 can have virtually any shape and size, but should include a rod-seating recess 225 formed therein that extends from a position distal to the proximal end 221 a of the upright portion through the second portion 227 to define the opposed arms 222 a, 222 b. The recess 225 is adapted to receive a rod that extends between the arms 222 a, 222 b in a direction substantially parallel to the direction of the arms 222 a, 222 b.

[0055] The arms 222 a, 222 b are similar to arms 22 a, 22 b shown in FIG. 1. Each arm 222 a, 222 b includes a semi-cylindrical wall 223 a, 223 b formed on proximal end thereof for contouring the head of an implant being engaged. The arms 222 a, 222 b are configured to fit within corresponding recesses or slots formed in the head of the implant. The slots in the implant (not shown should be positioned in a distal portion of each leg of a U-shaped head of an implant. This configuration allows the rod to be aligned with the rod-receiving portion in the head of the implant.

[0056] The rod-engaging member 218 is shown in more detail FIG. 10, and is effective to push a spinal rod toward an implant being grasped by the grasping member 214. The rod-engaging member 218 can have a variety of configurations, but as shown has a generally rectangular shape and includes opposed proximal and distal ends 240, 242. The proximal end 240 is mated to or integrally formed on the distal end of the rod-pusher member 216, and the distal end 242 is adapted to receive a spinal rod. The distal end 242 preferably includes a recess 244 formed therein for seating the spinal rod to facilitate reduction of the rod toward the implant being engaged by the grasping member 214. The recess 244 should extend in the same direction as the arms 222 a, 222 b of the grasping member 214 to allow a rod to be positioned between the arms 222 a, 222 b and seated in the recess 244.

[0057] In use, the device 210 is operated in the same manner as device 10, except that the implant is grasped in a different direction. In particular, device 10 grasps the implant beneath the rod-receiving recess formed in the U-shaped head of an implant, while device 210 grasps the implant along each leg of the U-shaped head. A person having ordinary skill in the art will appreciate that modifications can be made to the rod approximator to allow an implant to be grasped at different locations and in different directions with respect to the U-shaped head.

[0058] FIGS. 11A-11C illustrate one embodiment of a spinal implant 100 for use with a rod approximator according to the present invention. As shown, the implant 100 includes a threaded shank 102 and a generally U-shaped head 104 having an open proximal end 104 a, and a closed distal end 104 b attached to the shank 102. Preferably, the shank 102 is rotatably mated to the distal end 104 b of the head 104 to allow rotation of the head 104. A variety of techniques can be used to allow rotation of the head with respect to the shank 102. By way of non-limiting example, the shank 102 can include an enlarged proximal portion (not shown) and can be disposed through a bore formed in the distal end 104 b of the head 104. The enlarged proximal portion will prevent the shank 102 from extending completely through the bore. Once a spinal rod is disposed within the U-shaped head and secured by a closure mechanism, the rod will prevent rotation of the head 104 with respect to the shank 102.

[0059] The U-shaped head 104 includes opposed side walls 114 a, 114 b that define a rod-receiving portion 108 for seating a spinal fixation rod, and that are substantially parallel to one another. The inner surface of the head 104 includes threads 112 formed thereon for mating with a closure mechanism effective to secure the rod in the rod-receiving portion 108 of the head 104, and the outer surface of the head 104 includes opposed recesses 106 a, 106 b formed therein for receiving the arms 22 a, 22 b of the grasping member 14. The recesses 106 a, 106 b extend in a direction transverse to the direction of the side walls 114 a, 114 b, and are preferably positioned just proximal to the distal end 104 b of the head 104. Thus, the recesses 106 a, 106 b are positioned distally adjacent to the cut out portions 115 a, 115 b that form the rod-receiving portion 108 of the head 104 of the implant 100: The recesses 106 a, 106 b can, however, be disposed in the distal portion of each side wall 114 a, 114 b to allow the implant to be grasped in an opposed direction. The position of the recesses 106 a, 106 b is particularly advantageous in that it facilitates engagement of the implant 100 by a rod approximator since the grasping member 14 does not need to grasp the implant 100 underneath the head 104. The position of the recesses 106 a, 106 b also avoids potential contact with adjacent bone structures.

[0060] Each recess 106 a, 106 b can have a variety of shapes and sizes, but preferably the recesses 106 a, 106 b are elongated slots which form upper and lower shoulders 108 a, 108 b. The upper and lower shoulders 108 a, 108 b can each be substantially planar, but preferably the lower shoulder 108 b is substantially planar and the upper shoulder 108 a is substantially planar but includes opposed ends 109 a, 109 b that are curved such that they extend away from the lower shoulder 108 b. The curved shape of the upper shoulder 108 a allows the arms 22 a, 22 b of the grasping member 14 to be inserted into the recesses 106 a, 106 b at an angle.

[0061] A person having ordinary skill in the art will appreciate that the implant 100 can have a variety of configurations, and that the features illustrates can be used on a variety of implants, includes hooks and other fastener devices.

[0062] In use, one or more spinal implants 100 are screwed into vertebral bone structures. Typically, where two spinal implants 100 are fastened into adjacent vertebra, a spinal rod is inserted into the rod-receiving portion 108 of each implant. However, due to the alignment of the implants 100, it can be difficult to position the rod within each rod-receiving recess 108. Thus, a rod approximator device is necessary. The rod approximator device 10 is used by inserting the arms 22 a, 22 b of the grasping member 14 into the corresponding recesses 106 a, 106 b of the head 104 of the implant 100. With the rod pusher member 16 in the first, proximal position, the device can be manipulated to place the spinal rod between the rod engaging member 18 and the head 104 of the implant 100. The first and second handle members 52, 54 can then be grasped and squeezed together to cause the rod pusher member 16 to move to the second, distal position, thereby causing the rod engaging member 18 to grasp and push the stabilizing rod into the rod-receiving recess 108 formed in the head 104 of the spinal implant 100. While maintaining the device 10 in the second, actuated position, a closure mechanism can be threaded into the head 104 of the spinal implant 100 to secure the stabilizing rod in the rod-receiving recess 108.

[0063] One of ordinary skill in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety. 

What is claimed is:
 1. A medical device for seating a stabilizing rod in a rod-receiving portion of a spinal implant, the device comprising: an elongate member having a proximal end and a distal end, and defining an axis extending therebetween; a grasping member extending from the distal end of the elongate member in a direction substantially transverse to the axis, the grasping member being effective to engage a spinal implant; a rod pusher member slidably mated to the elongate member and movable along the axis between a first position in which the rod pusher member is positioned a distance apart from the grasping member and is effective to grasp a stabilizing rod, and a second position in which the rod pusher member is positioned adjacent to the grasping member and is effective to position the grasped stabilizing rod in a rod-receiving portion of a spinal implant being engaged by the grasping member; and an actuating member coupled to the proximal end of the elongate member and effective to move the rod reduction member with respect to the grasping member.
 2. The device of claim 1, wherein the actuating member comprises opposed first and second members, and wherein a force applied to bring the first and second members toward one another is effective to move the rod pusher member from the first position to the second position.
 3. The device of claim 1, wherein the actuating member extends in a direction substantially transverse to the axis.
 4. The device of claim 3, wherein the actuating member extends in a direction opposed to the grasping member.
 5. The device of claim 1, wherein the grasping member defines opposed arms adapted to slide into and engage corresponding slots formed in a spinal implant.
 6. The device of claim 1, wherein the rod pusher member comprises: a shaft having proximal and distal ends, and being slidably mounted on the elongate member along the axis; and a rod-engaging member mated to the distal end of the shaft and offset a distance apart from the shaft in a direction substantially transverse to the axis.
 7. The device of claim 6, wherein the rod-engaging member has a substantially semi-cylindrical shape and includes at least one rod-engaging recess formed on a distal facing portion thereof.
 8. The device of claim 7, wherein the grasping member defines opposed arms adapted to slide into and engage corresponding slots formed in a spinal implant.
 9. The device of claim 8, wherein the at least one rod-engaging recess formed in the rod-engaging member is axially aligned with the opposed arms of the grasping member.
 10. The device of claim 6, wherein the actuating member comprises a first, stationary member mated to the proximal end of the shaft, and a second, opposed movable member mated to the proximal end of the elongate member, and wherein a force applied to bring the second, movable member toward the first, stationary member is effective to move the rod-engaging member from the first position to the second position.
 11. The device of claim 1, wherein the distal end of the elongate member includes a bent portion effective to position the grasping member a distance apart from the elongate member.
 12. The device of claim 11, wherein the bent portion extends at about a 45° angle with respect to the axis.
 13. The device of claim 1, wherein the actuating member includes a ratchet mechanism effective to move the rod pusher member from the first position to the second position in predetermined increments.
 14. The device of claim 13, further comprising a release mechanism coupled to the ratchet mechanism and effective to release the ratchet mechanism to enable the rod pusher member to return to the first position.
 15. A system for seating a stabilizing rod in a rod-receiving portion of a spinal implant, comprising: a spinal implant having a distal, bone engaging portion, and a proximal head including a base portion mated to the distal, bone engaging portion, and a rod-receiving recess formed in the proximal head for seating a stabilizing rod; and a rod reduction device including an elongate member having a distal grasping member offset from a longitudinal axis of the elongate member, the grasping member being adapted to engage the base portion of the head of the spinal implant and to grasp the spinal implant, and a rod pusher member slidably mounted on the elongate member and effective to grasp a stabilizing rod and, upon actuating, to push the rod into the rod-receiving recess formed in the spinal implant.
 16. The system of claim 15, wherein the distal grasping member is substantially U-shaped.
 17. The system of claim 16, wherein the base portion of the head includes opposed slots formed therein, and wherein the grasping member is adapted to slide into the slots to grip the implant.
 18. The system of claim 15, wherein the opposed slots formed in the base portion of the head of the spinal implant each include an upper and lower shoulder, and wherein the lower shoulder is substantially planar, and the upper shoulder is substantially planar and includes opposed ends that are curved in a direction away from the lower shoulder.
 19. The system of claim 15, wherein the head of the spinal implant has a substantially hollow, cylindrical shape and includes opposed cut-out portions that form the rod-receiving recess for seating a stabilizing rod.
 20. The system of claim 19, wherein the opposed slots formed in the base portion of the head of the spinal implant are positioned distally adjacent to the opposed cut-out portions formed in the head of the spinal implant.
 21. The system of claim 19, wherein the rod pusher member comprises an elongate shaft having proximal and distal ends that extend along the longitudinal axis, and a rod-engaging member mated to the distal end of the shaft and offset a distance apart from the axis of the shaft.
 22. The system of claim 21, further comprising an actuating member mated to the elongate member and the rod pusher member, the actuating member being effective to selectively move the rod pusher member between a first position in which the rod-engaging member is offset a distance apart from the grasping member, and a second position in which the rod-engaging member is positioned adjacent to the grasping member and is effective to position a stabilizing rod in the rod-receiving recess formed in the head of the spinal implant that is being engaged by the grasping member.
 23. The system of claim 21, wherein the actuating member extends in a direction substantially transverse to the axis.
 24. The system of claim 23, wherein the actuating member extends in a direction opposed to the grasping member.
 25. The system of claim 22, wherein the actuating member comprises opposed first and second members, and wherein a force applied to bring the first and second members toward one another is effective to move the rod pusher member from the first position to the second position.
 26. The system of claim 25, wherein the first member is a stationary member mated to the proximal end of the elongate shaft, and wherein the second, opposed member is a movable member mated to the proximal end of the elongate member.
 27. The system of claim 22, wherein the actuating member comprises a ratchet mechanism effective to move the rod pusher member from the first position to the second position in predetermined increments.
 28. The system of claim 27, further comprising a release mechanism coupled to the ratchet mechanism and effective to release the ratchet mechanism to enable the rod pusher member to return to the first position.
 29. The system of claim 19, wherein the grasping member defines opposed arms adapted to slide into and engage the corresponding slots formed in the head of the spinal implant.
 30. The system of claim 21, wherein the rod-engaging member includes at least one rod-engaging recess formed on a distal facing portion thereof.
 31. The system of claim 30, wherein the rod-engaging member has a semi-cylindrical shape that is adapted to receive and contour a portion of the head of the spinal implant.
 32. The system of claim 21, wherein the rod-engaging member includes a central opening to enable access to the rod-receiving recess of the spinal implant.
 33. The system of claim 21, wherein the grasping member defines opposed arms adapted to slide into and engage corresponding slots formed in a spinal implant.
 34. The system of claim 33, wherein the at least one rod-engaging recess formed in the rod-engaging member is axially aligned with at least one of the opposed arms of the grasping member.
 35. The system of claim 15, wherein the elongate member includes a bent portion effective formed at a distal end thereof and effective to position the grasping member a distance apart from the elongate member.
 36. The system of claim 35, wherein the bent portion extends at about a 45° angle with respect to the axis.
 37. A spinal implant, comprising: a head member having a substantially hollow, cylindrical shape and including an open, proximal end and a closed, distal end, and a rod-receiving recess formed from opposed cut-out portions extending from the open, proximal end and terminating proximal to the closed, distal end, the head further including opposed slots formed in a base of the head proximal to the closed, distal end and distal to the cut-out portions, the opposed slots being effective to receive opposed arms of a rod reduction device to enable the rod reduction device to engage the head of the spinal implant and to engage a stabilizing rod to push the rod into the rod-receiving recess formed in the head of the spinal implant; and a bone-engaging member extending from the closed, distal end of the head member and effective to engage bone.
 38. The spinal implant of claim 37, wherein the opposed slots formed in the base portion of the head of the spinal implant each include an upper and lower shoulder, and wherein the lower shoulder is substantially planar, and the upper shoulder is substantially planar and includes opposed ends that are curved in a direction away from the lower shoulder.
 39. A method for reducing a stabilizing rod into a rod-receiving portion of a spinal implant, comprising the steps of: providing at least one spinal implant having a distal, bone engaging portion, and a proximal head including a rod-receiving recess formed therein for seating a stabilizing rod, the proximal head including a base portion having opposed slots formed therein; providing an elongate stabilizing rod adapted to seat in the rod-receiving recess of the at least one spinal implant; providing a rod reduction device including an elongate member having a distal, grasping member adapted to slide into the slots formed in the base portion of the head of the spinal implant and to grasp the spinal implant, a rod pusher member slidably mounted on the elongate member and effective to grasp the stabilizing rod and push the rod into the rod-receiving recess formed in the spinal implant, and an actuating member mated to the elongate member and the rod pusher member, the actuating member being effective to move the rod pusher member between a first position in which the rod pusher member is offset a distance apart from the grasping member, and a second position in which the rod pusher member is positioned adjacent to the grasping member; engaging the head of the spinal implant by positioning the grasping member of the rod reduction device in the opposed slots formed in the base portion of the head of the spinal implant; manipulating the rod reduction device to enable the rod pusher member to grasp and engage the stabilizing rod; actuating the actuating member to move the rod pusher member from the first position to the second position, thereby causing the rod pusher member to push the stabilizing rod into the rod-receiving recess formed in the head of the spinal implant; and applying a closure mechanism to the head of the spinal implant to secure the stabilizing rod in the rod-receiving recess. 